Re: [Harp-L] Sorry, it's combs again




----- Original Message ----- From: "Steve Baker" <steve@xxxxxxxxxxxxx>
To: "Harp-L" <harp-l@xxxxxxxxxx>
Sent: Monday, September 22, 2008 9:24 AM
Subject: [Harp-L] Sorry, it's combs again



Thanks Brendan for your thoughtful contribution to this discussion. This still seems to me to raise the question, what exactly is it that the player is perceiving as different? Suave Blues Man's suggestion to test this objectively seems to me the only way to go from here.

During my comparison of around two dozen otherwise identical combs with specific differences in material and finish, using identical covers and the same two sets of reed plates, my notes showed consistent differences in sound. I have no doubt that these differences actually exist, and even though they are relatively small and may not be noticeable to the listener, I notice them. I assume they are the result of slightly different acoustic overtone profiles, which will be measurable in the same way as for example the sound of stainless steel reeds is verifiably different from the sound of brass reeds, even though most listeners won't notice the difference. How or whether the difference is perceived and interpreted (or not) by the listener doesn't necessarily have any bearing on whether or not it actually exists.

If you conducted your comparison in private and you knew the material in the harp when you played it, then it is easy for your expectations to affect the data. I do not exempt myself from this tendency. It is human nature. That is why there are double-blind comparisons of drugs and beverage tastes.

In Vol 61/83 Ken (Mojo Red) mentioned our comparison at SPAH between his MB Deluxe fitted with the brass comb and my standard MBDL. Not surprisingly, his one was noticeably louder than the harp with the wooden comb, which is after all one of the reasons why people spend a load of money on metal combs.

Metal combs are better because they are more dimensionally stable and their screw threads are stronger.


I presume the difference is caused by the fact that the acoustic conductivity of brass is higher than that of wood and the inner surfaces reflect sound waves more strongly, both of which contribute to making the instrument sound louder and brighter.

The comb plays no perceptible role in the generation. bsorption, or transmission of the sound. If it did, listeners could perceive differences.



In order to document the effect of comb material on sound it should only be necessary to play the same sustained single notes with the same air pressure and size of air column on all test combs (using the same reed plates in each case) while recording the overtone profile and the volume. The harmonica can easily be blown/drawn mechanically, which ought to satisfy even the most hardened sceptics. I have arranged to run tests later this year in the Hohner acoustics lab to objectively measure any differences and will post the results here, so maybe we can then finally lay this subject to rest,

Please publish the conditions of the test. How many harps, how many players/listeners, how many times the harps were played, how are the sequence of plays randomized, what provisions to deny the players/listeners knowledge of the materials, etc. Remember, the question is not about ~any~ differences, it is about the ability of listeners and players to ~perceive~ the differences.


Vern
Visit my harmonica website www.Hands-Free-Chromatic.7p.com


Steve


Steve Baker
steve@xxxxxxxxxxxxx
www.stevebaker.de
www.bluesculture.com
www.youtube.com/stevebakerbluesharp

_______________________________________________
Harp-L is sponsored by SPAH, http://www.spah.org
Harp-L@xxxxxxxxxx
http://harp-l.org/mailman/listinfo/harp-l





This archive was generated by a fusion of Pipermail 0.09 (Mailman edition) and MHonArc 2.6.8.